Germ cells (vasa, magenta), Hub (asterisk or Fas3, white). (A) Wild-type GSCs are tightly associated with the hub. (B) Two days after germline stat depletion (Tj Gal4/UAS HA-stat; statF/stat85c9), GSCs became displaced from the hub. (C–F) 8 days after germline stat depletion, germ cells nearest the hub accumulate M5-4 lacZ (C, white, arrows), have spherical or dumbbell-shaped spectrosomes (D, α-spectrin, green, arrows; D′ shows α-spectrin alone), and undergo mitosis as individual cells (E, phosphohistoneH3, green, arrow; a mitotic CySC is also present), all consistent with GSC identity. M5-4 lacZ (C, white) also accumulates in the hub (arrowheads), but not in CySCs (Tj, green), indicating CySCs do not take on hub fate. (F) stat-depleted GSCs fail to reliably orient mitotic spindles away from the hub (centrosomin reveals centrosomes, green). Two mitotic germ cells outlined, one oriented (arrow) and one non-oriented (arrowhead). (G) With germline stat depletion, the hub became surrounded by CySCs (Zfh-1, green). (H) Testes with Gal4-driven stat in the CySC lineage (Tj Gal4/UAS stat; stat85c9/+) undergo modest GSC loss, but still maintain GSCs at the hub (arrows, Zfh-1, green). (I) Germline RNAi knockdown of stat (nos gal4 VP16 VDRC 106980) caused GSCs to be displaced from the hub, and the hub became surrounded by CySCs (Zfh-1, green). Bar:10μm.